title: The transition-like state and Pi entrance into the catalytic a subunit of the biological engine A-ATP synthase.
abstract: Archaeal A-ATP synthases catalyze the formation of the energy currency ATP. The chemical mechanisms of ATP synthesis in A-ATP synthases are unknown. We have determined the crystal structure of a transition-like state of the vanadate-bound form of catalytic subunit A (A(Vi)) of the A-ATP synthase from Pyrococcus horikoshii OT3. Two orthovanadate molecules were observed in the A(Vi) structure, one of which interacts with the phosphate binding loop through residue S238. The second vanadate is positioned in the transient binding site, implicating for the first time the pathway for phosphate entry to the catalytic site. Moreover, since residues K240 and T241 are proposed to be essential for catalysis, the mutant structures of K240A and T241A were also determined. The results demonstrate the importance of these two residues for transition-state stabilization. The structures presented shed light on the diversity of catalytic mechanisms used by the biological motors A- and F-ATP synthases and eukaryotic V-ATPases.
authors.affiliation: Nanyang Technological University, School of Biological Sciences, 60 Nanyang Drive, Singapore 637551, Republic of Singapore.
authors.forename: Malathy Sony Subramanian
authors.initials: MS
authors.lastname: Manimekalai
authors.forename: Anil
authors.initials: A
authors.lastname: Kumar
authors.forename: Jeyaraman
authors.initials: J
authors.lastname: Jeyakanthan
authors.forename: Gerhard
authors.initials: G
authors.lastname: Grüber
mesh_terms: D025181:ATP Synthetase Complexes / Q000737:chemistry*; D000255:Adenosine Triphosphate / Q000737:chemistry / Q000378:metabolism; D000595:Amino Acid Sequence; D001665:Binding Sites; D002384:Catalysis; D020134:Catalytic Domain; D018360:Crystallography, X-Ray; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011487:Protein Conformation; D021122:Protein Subunits / Q000737:chemistry; D043902:Pyrococcus horikoshii / Q000201:enzymology*; D025262:Vacuolar Proton-Translocating ATPases / Q000737:chemistry; D014638:Vanadates / Q000737:chemistry
chemical_list: D021122:Protein Subunits; D014638:Vanadates; D000255:Adenosine Triphosphate; D025181:ATP Synthetase Complexes; D025262:Vacuolar Proton-Translocating ATPases